This species of colchicums is hardy through upper New York, along the New England coast and to the Great Lakes (Zone 4). Its range includes areas where it seldom gets colder than -10° to -20°F.
Locating And Planting
Plant colchicums in a sunny location as soon as you buy them during their brief dormant period in July and August. Like most bulbous plants, colchicums require soil that drains well after rains. They do poorly in wet, clayey soils. If necessary, build colchicum beds higher than the surrounding soil surface, add lots of organic matter such as chopped leaves or commercially sold peat humus to the soil to improve drainage. Slightly acidic soil (pH 6.0 to 6.5) is fine.
Plant corms 3 to 4 inches deep and 3 to 4 inches apart. Measure the depth from the bottom of the hole. With the corms' pointed growing tips right-side-up, press their rounded bottoms into the soil, using a slight twisting motion to assure good soil contact for the root plate. Plant corms in groups of 6 to 8. Cover the bed with mulch to protect the soil from extreme variations in temperature which may cause it to heave and disturb the bulbs. Try "naturalizing" colchicum plantings by scattering the corms informally and planting them where they fall.